Cycles viewport render different than f12 render?
The flower mesh has a solidify modifier which is only enabled for rendering. The extra thickness from this modifier makes the translucent material give a different result.

In general for differences between render and viewport, check these:


Object viewport and render visibility in the outliner
Modifier viewport and render visibility
Particles and hair resolution settings
Curve, surface and metaball tessellation settings
Render layer settings
Color management settings
Compositing nodes and sequencer strips